Seal material



March 15, 1960 R. H. BAsKl-:Y

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O g INVENTOR RAYMOND H. BA SKEY BYXMM ATTORNEY United States APatentSEAL MATERIAL Raymond H. Baskey, Lakewood, Ohio, assignor to HorizonsIncorporated, Cleveland, Ohio, a corporation of New Jersey ApplicationJune 20, 1958, Serial No. 743,375 n 4 claims. (ci. z91sz.s)

mium nitride bonded with nickel and infiltrated withsilver.

There are many important applications wherein materials are subjected torubbing, either continuously. or intermittently, and particularly thoseapplications wherein it is difficult or even impossible to provide alubricant to the contact area. Such applications include inaccessibleportions of rotating shafts, for example. The problem is renderedparticularly acute in instances in which the surfaces are exposed tohigh temperatures, and for corrosive environments, and are required tofunction at high speeds.

In the past, seal materials have been sought which would function in theabsence of any external lubrication, possibly through the formation of astable lm on the components Wearing against one another-or by othermechanisms not fully understood.

By the present invention there is lpresented a material suitable forrotating seal components subjected to operation: at temperatures of upto about l350 F.; at slidinng speeds of up to about 30,000 feet perminute; at loads up to about 14 pounds per square inch gage; and underservice conditions wherein no liquid or solid (powder) lubricant couldbe supplied to the surfaces.

Figures 1 and 2 show graphically, wear rates of certain materials atvarious test temperatures.

In an earlier copending application for patent, Serial No. 585,859 tiledMay 18, 1956, and now issued as United States Patent 2,875,510, thereare described compositions consisting of between 45% and 82% by weightof nickel, between about 3% by weight and 20% by weight of a refractoryboride and the balance essentially all silver or a silver base alloy.Such compositions were found to provide improved bearing materials. Inthe present invention, instead of a composition predominantly consistingof nickel, there is provided a material, the major proportion of whichconsists of chromium nitride, and which includes smaller amounts ofnickel and silver. Thus, like the earlier disclosed invention, amaterial with a duplex structure is used to provide a low-friction,lowwear combination, but unlike the earlier application, the harderphase predominates in the compositions of this invention.

In brief, in accordance with the present invention, compositions havebeen devised consisting primarily of chromium nitride, bonded by meansof nickel and including silver as a lubricating phase. Thesecompositions lhave been tested against speciall surfaces, as described'ice ing the present invention were evaluated, consisted of a tool steeland a nickel base Inconel having the following compositions:

Tool Steel Inconel W-5.75%. (NomlnalComposltlon). (Jr-4.10%. Cr--l4.l7%.Mo-5.25%. Iii-3.0%. Stv-9.0%. Fe-1.5%. V-1.90%. C0.4%. C-O.89%. BalanceNi, except lor Balance Fe, except for impurities.

impurities. Y

' ing and infiltration could be accomplished in a single heating step.`Attempts to lill all of the pores by adding all of the'silver byiniiltration of a silver-free preform were inelectual, possibly becauseof a reluctance to wet one or more of the other constituents of thecomposition.

Essentially the procedure found to be suitable consisted of thefollowing steps:

(l) A mixture was formed of chromium nitride, silver powder and nickelpowder. The silver was preferably minus 325 mesh (Tyler Standard), thenickel was minus 200 mesh to plus 325 mesh, and the nitride was equallyline. By using such finely divided powders, intimacy of mixing wasfacilitated.

(2) The mixedV powders were placed in a die and pressed at 25 tons persquare inch to give a cylindrical specimen. Pressures between 20 tonsper square inch and 35 tons per square inch would appear to be equallysatisfactory, depending on the specimen size and conguration.

(3) Silver, in an amount somewhat in excess of that required tocompletely infiltrate the compact to density was placed in physicalcontact with the compact, and preferably on top of the compact.

(4) The compact and silver were heated at temperatures of about 1l50 C.for about two (2) hours under a dry hydrogen atmosphere, to melt thesilver and permit it to be absorbed into the pores of the compact.

(5) The resulting specimen Was examined for homogeneity, phases, densityand appearance and then machined to the desired shape and size.

The resulting material was found to contain 4 phases: a nickelrich-chromium nitride phase having a Vickers hardness of between about700 and 1000; a chromium nitride phase; a nickel phase; and a silverphase.

For purposes of comparison the wear rate of one chromium nitridecomposition is shown relative to the wear rate of a similar refractorybased composition, in the drawings in which:

Figure l is a graph of wear rates against a tool steel at varioustemperatures and Figure 2 is a graph of wear rates against Inconel atvarious temperatures.

Other compositions were prepared land tested and it was found that therelative proportions of chromium nitride, nickel and silver could bevaried over a substantial range without impairing the eiectiveness ofthe material at elevated temperatures. Thus when employing Y Patented,Main v15, 196i)AV y 1. A? seal material consisting essentially of.betwn 50% and 70% by Weight-of chromium nitrideand from 20% to30%byweghtl0flnickel and the balance being silver saidsilvervconstituting between 10% and'20% by weight of the seal materialcomposition.

2. A compositionof'matter possessing superior wear resistance cproperties atleleyatedtemperatures and con- 4 v sisting of between 50and 70% by weight of chromium nitride, between about 20% and 30% byweight of nickel and the balance substantiallyy all silver said silvercomprising from 10% to 20% by weight of the composition. 3. A Wearresistant composition of matter consisting essentially of about 60% byweight of chromium nitride and the remainder being equalparts of nickeland silver by weight.

4. A sintered composition of matter composed of between about20%and/.30%2by1weight of nickeL about 60% of chromium *nitrideI and-therbalance ysubstantially all silver.

References Cited in the le of this patent UNITED STATES PATENTS MarthMay 3, 1938 Hoyer YSept. 9, 1958

1. A SEAL MATERIAL CONSISTING ESSENTIALLY OF BETWEEN 50% AND 70% BY WEIGHT OF CHROMIUM NITRIDE AND FROM 20% TO 30% BY WEIGHT OF NICKEL AND THE BALANCE BEING SILVER SAID SILVER CONSTITUTING BETWEEN 10% AND 20% BY WEIGHT OF THE SEAL MATERIAL COMPOSITION. 